Our primary goal is to isolate and study mutations in Drosophila which lead to neoplastic changes or may affect neoplastic changes that have been initiated. In order to make the approach an analytical rather than descriptive one, we are concentrating our efforts on collecting a large number of such mutations. In this way we hope to deal with general features of neoplasia rather than to become too involved at this stage with the description of any one phenotype. We have developed a number of novel selection techniques to isolate neoplastic mutants. We have also devised a method to isolate temperature-sensitive mitotic arrest mutants. Several such mutants have been isolated and are now being analyzed. We are introducing cells with malignant properties into a cell population by means of X-ray induced somatic recombination and gynandromorphs. We have discovered that cells of one neoplastic mutant which behave autonomously in intact tissue transplants, behave nonautonomously in genetic mosaics. In some way adjacent normal cells overcome the defect caused by the mutation, a matter we are now investigating. We also plan to employ temperature-sensitive neoplastic mutants to initiate neoplastic transformations at specific stages of development. These techniques are enabling us to examine the interaction of normal and neoplastic cell populations and also to investigate intercellular communication among normal and neoplastic cells. The results obtained thus far encourage us to believe that Drosophila, a rather unconventional organism in cancer biology, may have important and unique contributions to make in this field.